Water quality measuring apparatus with a sensing wafer clamped between two o-rings

ABSTRACT

A device for water quality measurement apparatus includes a plurality of multi-element arrays formed on a substrate, which are immersed in a solution for detecting electroactive elements or compounds present in such a solution. A wafer is located between first and second ‘O’ rings, with the first ‘O’ ring being disposed on a first side of the wafer and the second ‘O’ ring being disposed on a second side of the wafer, opposite to the first side. The first and second ‘O’ rings are arranged such that the wafer is exposed to substantially equal pressure on both sides.

BACKGROUND OF THE INVENTION

The present invention relates to water quality measurement apparatus.More specifically the present invention relates to an improvedmechanical arrangement for water quality measurement apparatus.

The use of a plurality of electrochemical sensors deposited on a singlewafer for the purpose of measuring multiple parameters of a liquidsample is well known. U.S. Pat No. 5,120,421 discloses anelectrochemical sensor which comprises a plurality of multi-elementarrays formed on a substrate, the sensor being immersed in a solutionfor detecting electroactive elements or compounds present in such asolution.

The main advantage of this type of sensor is that it is capable ofmeasuring multiple parameters of a liquid sample. In addition, it issmall, cheap to manufacture, and disposable. A primary use for suchsensors is for on-line measurements to be made in a mains water pipe,thus eliminating the need to collect a sample and return to thelaboratory for analysis, which is costly, time-consuming and oftenresults in substantial errors in measurement accuracy.

To be able to conduct on-line, in-situ type measurements, the sensormust be exposed to the water in the pipe. This is achieved by a knowntechnique in which a specially adapted mechanical device is fitted tothe water pipe. This device allows for the sensor to be inserted intothe pipe in such a way that the sensing area of the wafer is exposed tothe water.

However, this known arrangement suffers from several disadvantages.Firstly the wafer is often inherently thin and may suffer damage or evenrupture if exposed to different amounts of pressure. For example, ifmains wafer pressure is present on one side of the wafer and atmosphericpressure present on the other side the difference between the two maycause the wafer to rupture. Secondly, any leakage of water from thesensor area to the electrical connectors can result in the sensorfailing.

SUMMARY OF THE INVENTION

The present invention offers substantial improvements to the knownmethods in which wafer type sensors are held in place within themechanical devices used with this type of water monitoring apparatus.

According to the present invention there is provided measuring apparatusincluding a wafer located between a first and a second ‘O’ ring, withsaid first ‘O’ ring being disposed on a first side of side of saidwafer, and said second ‘O’ ring being disposed on a second side of saidwafer, said second side being opposite to said first side, said firstand said second ‘O’ rings being arranged such that in use a centralportion of said first side of said wafer and a central portion of saidsecond side of said wafer being of substantially the same diameter andopposite said central portion of said first side are exposed tosubstantially equal pressure and any remaining portions of said firstand said second sides located outside said central portions are exposedto substantially equal pressure, said apparatus further including amechanical device arranged to hold said wafer proximate a distal endthereof by means of said first ‘O’ ring and said second ‘O’ ring, saidfirst and said second ‘O’ rings being removably attached to a first anda second ‘O’ ring holding means respectively, with said first ‘O’ ringholding means being substantially fixed to said distal end of saidmechanical device, and said second ‘O’ ring holding means beingsubstantially fixed to a detachable block means with said detachableblock means being arranged to be held in place at said distal end ofsaid mechanical device such that said wafer is held proximate saiddistal end of said mechanical device, characterised in that said first‘O’ ring holding means further includes a plurality of pins disposedwithin a circular area defined by said first ‘O’ ring and whichcorresponds substantially with said central portion of said first sideof said wafer, with said plurality of pins arranged to facilitateelectrical contact between a plurality of electrical contact pointsdisposed on said first side of said wafer and located within saidcentral portion of said first side of said wafer and further electricalcontacts disposed within said mechanical device.

In yet a further embodiment said first ‘O’ ring holding means includes agroove into which said first ‘O’ ring substantially fits.

In yet a fierier embodiment said second ‘O’ ring holding means includesa groove into which said second ‘O’ ring substantially fits.

Said plurality of pins may be spring loaded pins.

As will be appreciated by a person skilled in the art, said plurality ofpins may be of a type other than spring loaded pin.

According to a further aspect of the present invention said wafer issubstantially flat.

According to a further aspect of the present invention said wafer issubstantially square.

According to yet a further aspect of the present invention said waferincludes a plurality of sensing devices disposed upon said first side ofsaid wafer.

According to yet a further aspect of the present invention saidplurality of sensors are disposed on both said first side and saidsecond side of said wafer.

In yet a further aspect of the present invention said central portionsof said wafer are exposed to equal amounts of atmospheric pressure andsaid remaining portions of said wafer are exposed to equal amounts ofwater pressure.

In yet a further aspect of the present invention said central portionsof said wafer are prevented from being exposed to water.

By exposing each side of the wafer to substantially equal amounts ofpressure, the wafer is less likely to rupture due to the effects ofunequal amounts of pressure. For example, if the central portion of oneside of the wafer was exposed to atmospheric pressure and the centralportion of the opposite side was exposed to water pressure, the wafer ismore likely to rupture due to the unequal pressure exerted on it then ifboth sides where exposed to equal amounts of either water or atmosphericpressure.

The apparatus according to the present invention advantageously allowsfor the wafer to be made thinner, while still being able to be used inapplications which expose the wafer to higher pressures. Furthermore,the present invention advantageously allows for sensor devices to bedisposed on both sides of said wafer.

While the principle application of the preferred embodiment of thepresent invention is as a water quality measurement apparatus, as willbe appreciated by those skilled in the art, measurement of other typesof anlaytes, such as solid, gases and liquids other than water, may bemade without departing from the scope of the present invention.

While the principle advantages and features of the present inventionhave been described above, a greater understanding and appreciation ofthe invention may be obtained by referring to the following drawings anddetailed description of a preferred embodiment, presented by way ofexample only.

BRIEF DESCRIPTION OF THE DRAWING.

FIG. 1 is a diagram of a wafer type sensor according to one aspect ofthe present invention,

FIG. 2 is a diagram of the opposite side of the wafer shown in FIG. 1,

FIG. 3 is a diagram of the mechanical device used for inserting thewafer into water pipes,

FIG. 4 shows a side view of the wafer held in place by the ‘O’ rings,according to a preferred embodiment of the present invention,

FIG. 5 shows a cross section of the probe head portion of the mechanicaldevice shown in FIG. 3; and

FIGS. 6a-c are respective end and side views of the probe head portionof FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a typical arrangement of a wafer according to a preferredembodiment of the present invention. In FIG. 1 a square wafer 10 isshown with a plurality of sensors 12 disposed on the surface. Eachsensor 12 is connected by a lead 14 to a plurality of correspondingelectrical contact points 16. As is well known in the art, themeasurement of various electrochemical properties in a liquid sample canbe achieved when a liquid sample comes into contact with the sensors 12.Known sensors are currently being used to measure various properties ofa liquid sample such as dissolved oxygen, pH, temperature, and Chlorineand Ammonia levels. The operation of these types sensors is well knownin the art, as disclosed in granted UK patents GB2283572 and GB2290617,which are hereby included as references.

The plurality of electrical contact point 16 are located within acentral portion 18 of wafer 10. The plurality of sensor devices 12,leads 14 and electrical contact points 16 are deposited using techniqueswhich are well known in the art such as thin and thick film depositionmethods. The wafer 10 remains substantially flat despite the presence ofsensors 12, leads 14 and contact points 16. The central portion 18 isthe area of the wafer which is enclosed by a first ‘O’ ring when thewafer is held in place within the mechanical device.

In this preferred embodiment the wafer 10 is substantially square. Acorner 17 of the wafer 10 is removed from the wafer. This allows forsimplified alignment of the wafer within the mechanical device. As willbe appreciated by those skilled in the art, the wafer 10 may be othershapes, such as circular or rectangular.

FIG. 2, where points also appearing in FIG. 1 bear identical numericaldesignation, shows the opposite side of the wafer 10 shown in FIG. 1. InFIG. 2 no sensors are disposed on this surface, however as would beappreciated by those skilled in the art, a plurality of sensors could bedisposed on this surface. The central portion 19 of the wafer in FIG. 2is substantially opposite to the central portion 18 of the wafer shownin FIG. 1. The central portion 19 is enclosed by a second ‘O’ ring whenthe wafer is held in place within the mechanical device. The effect ofplacing said first and second ‘O’ rings on opposite sides of the waferis to expose the central portions 18 and 19 to equal amounts ofpressure. Furthermore, the areas outside the central portion of thewafer are also exposed to equal amounts of pressure. The effect ofequalising the pressure on either side of the wafer is to reduce thelikelihood of the wafer rupturing during operation.

FIG. 3, where parts also appearing in FIGS. 1 and 2 bear identicalnumerical designation, shows a mechanical device 20 attached to a pipe22 for the purpose of allowing wafer 10 to be exposed to the water 24flowing through pipe 22. The pipe may be a mains water pipe. Themechanical device 20 includes a probe head 26 and a centrally locatedhollow movable tube 25. The probe head 26 is disposed at the distal endof the hollow tube 25, which is inserted into a housing 27. Themechanical device 20 is attached to the pipe 22 at the probe head endand is held in place, for example, by a clamping or threading means (notshown), which are both well known in the art. The wafer 10 is attachedto the probe head 26. The hollow tube allows for various electricalconnections such as power to be made to the wafer.

The mechanical device 20 further comprises a valve means 28 which whenin its closed position isolates the bottom end 27 a from the top end 27b of the housing 27. The valve 28 can only be closed when the hollowtube 25 is withdrawn from the bottom end 27 a of the housing 27. Inoperation, the hollow tube 25 may be withdrawn from the bottom end 27 aof the housing 27 for maintenance purposes or to replace the wafer. Whenthe valve 28 is in its open position the hollow tube 25 can be pushedinto the pipe 22 where the wafer is exposed to water and measurementscan be taken. FIG. 3 shows the mechanical device 20 in its measurementmode, with the probe head 26 and wafer 10 inserted into the bottom end27 a of the housing 27 and exposed to the water 24 located in the pipe22.

In FIG. 4, where parts also appearing in FIGS. 1, 2 and 3 bear identicalnumerical designation, a side view of wafer 10 is shown. A plurality ofsensors 12 are disposed on the surface 10 a of the wafer 10. The sensorsare disposed outside the area defined by a centrally located first ‘O’ring 34.

First ‘O’ ring 34 is removably attached to a first ‘O’ ring holdingmeans 35. First ‘O’ ring holding means 35 may be made of metal orplastic or other suitable material. First ‘O’ ring holding means 35 maycontain a groove (not shown) into which first ‘O’ ring 34 fits. Aplurality of spring pins 36 are disposed on first ‘O’ ring holding means35 and are located inside the diameter of first ‘O’ ring 34. Theplurality of spring pins 36 are arranged to extend substantiallyperpendicular from first ‘O’ ring holding means 35 in a manner whichfacilitates electrical contact with the plurality of contact points 16located on wafer 10.

A second ‘O’ ring 37 is removably attached to a second ‘O’ ring holdingmeans 38 which may be made of metal or plastic or other suitablematerial. Second ‘O’ ring holding means 38 may contain a groove (notshown) into which second ‘O’ ring 37 fits.

Wafer 10 is held in place by the first and second ‘O’ rings 34 and 37 ina manner such that wafer areas 18 and 19 are exposed to substantiallythe same amount of pressure and wafer areas 43 and 44 are also exposedto substantially the same amount of pressure.

In this preferred embodiment, during operation, wafer areas 18 and 19are exposed to atmospheric pressure and wafer areas 43 and 44 areexposed to water pressure. The water pressure will depend on the waterpressure in the water pipe 24 to which mechanical device 20 is attached.The seal created by ‘O’ rings 34 and 37 with the wafer must besubstantial enough to prevent leakage of water into wafer areas 18 and19.

In FIG. 5, where points also appearing in FIGS. 1-4 bear identicalnumerical designation, a more detailed view of the probe head 26 isshown. The probe head 26 has an opening 50 at one end. Wafer 10 isinserted in the opening 50 such that the plurality of electrical contactpoints 16 make electrical contact with the plurality of spring pins 36.Second ‘O’ ring holding means 38 is then inserted into probe opening 50.The second ‘O’ ring holding means 38 is held in place in the probe head26 via bayonet or thread means in a manner such that second ‘O’ ring 37makes contact with the wafer. The second ‘O’ ring holding means 38 isdesigned such that water to be analysed can enter the probe head viaopenings 50 and make contact with the plurality of sensors 12 disposedon wafer 10. Spring pins 36 extend inside probe head 26 and make furtherelectrical contact with various power and control electronics locatedoutside the mechanical device.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. Measuring apparatus comprising: a wafer located between first and second ‘O’ rings, said first ‘O’ ring being disposed on a first side of said wafer and said second ‘O’ ring being disposed on a second side of said wafer opposite to said first side, said first and said second ‘O’ rings being arranged such that in use a central portion of said first side of said wafer and a central portion of said second side of said wafer being of substantially the same diameter and opposite said central portion of said first side are exposed to substantially equal pressure and any remaining portions of said first and said second sides located outside said central portions are exposed to substantially equal pressure; a mechanical device arranged to hold said wafer proximate a distal end thereof by means of said first ‘O’ ring and said second ‘O’ ring, said first and said second ‘O’ rings being removably attached to a first and a second ‘O’ ring holding means respectively, with said first ‘O’ ring holding means being substantially fixed to said distal end of said mechanical device, and said second ‘O’ ring holding means being substantially fixed to a detachable block means which is arranged to be held in place at said distal end of said mechanical device, such that said wafer is held proximate said distal end of said mechanical device; wherein, said first ‘O’ ring holding means further includes a plurality of pins disposed within a circular area defined by said first ‘O’ ring and which corresponds substantially with said central portion of said first side of said wafer; and said plurality of pins are arranged to facilitate electrical contact between a plurality of electrical contact points disposed on said first side of said wafer and further electrical contacts disposed within said mechanical device.
 2. Apparatus as claimed in claim 1, wherein said first ‘O’ ring holding means includes a groove into which said first ‘O’ ring substantially fits.
 3. Apparatus as claimed in claim 1, wherein said second ‘O’ ring holding means includes a groove into which said second ‘O’ ring substantially fits.
 4. Apparatus as claimed in claim 1, wherein said plurality of pins are spring loaded pins.
 5. Apparatus as claimed in claim 1, wherein said wafer is substantially flat.
 6. Apparatus as claimed in claim 1, wherein said wafer is substantially square.
 7. Apparatus as claimed in claim 1, wherein said wafer includes a plurality of sensing devices disposed upon said first side of said wafer.
 8. Apparatus as claimed in claim 7, wherein said plurality of sensors are disposed on both said first side and said second side of said wafer.
 9. Apparatus as claimed in claim 1, wherein said central portions of said wafer are exposed to equal amounts of atmospheric pressure and said remaining portions of said wafer are exposed to equal amounts of water pressure.
 10. Apparatus as claimed in claim 1, wherein said central portions of said wafer are prevented from being exposed to water. 